Numerical simulations predict that metal-poor gas accretion from the cosmic web fuels formation of disk galaxies. This paper discusses how controls star formation, and summarizes physical properties expected for accreted by The also collects observational evidence sustaining formation. It reviews inferred neutral ionized hydrogen, as well stars. A number characterizing large samples star-forming galaxies can be explained accretion, in particular, relationship among stellar mass, metallicity,...

We present an automated morphological classification in 4 types (E,S0,Sab,Scd) of ~700.000 galaxies from the SDSS DR7 spectroscopic sample based on support vector machines. The main new property is that we associate to each galaxy a probability being four classes instead assigning single class. therefore better adapted nature where expect continuos transition between different types. algorithm trained with visual and then compared several independent classifications including Galaxy Zoo...

We have discovered small whirlpools in the Sun, with a size similar to terrestrial hurricanes (≲0.5 Mm). The theory of solar convection predicts them, but they had remained elusive so far. vortex flows are created at downdrafts where plasma returns interior after cooling down, and we detect them because some magnetic bright points (BPs) follow logarithmic spiral on their way being engulfed by downdraft. Our disk-center observations show 0.9 × 10−2 vortexes per Mm2, lifetime order 5 minutes,...

Abstract The claimed detection of a diffuse galaxy lacking dark matter represents possible challenge to our understanding the properties these galaxies and formation in general. galaxy, already identified photographic plates taken summer 1976 at UK 48-in Schmidt telescope, presents normal distance-independent (e.g. colour, velocity dispersion its globular clusters). However, distance-dependent quantities are odds with those other similar galaxies, namely luminosity function sizes clusters,...

This paper is the second in a series that models photospheric magnetic structures terms of atmospheres having optically thin fluctuations field and thermodynamic state (the MISMA hypothesis). We apply an inversion procedure to polarization Fe I λ6301.5 λ6302.5 observed network internetwork regions with Advanced Stokes Polarimeter. Some 5200 independent spectra, comprising mildly asymmetric very abnormal profiles, were reproduced by single type model atmosphere. It has three components, two...

view Abstract Citations (137) References (49) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observation and Interpretation of the Asymmetric Stokes Q, U, V Line Profiles in Sunspots Sanchez Almeida, J. ; Lites, B. W. We present a first approach to systematic characterization interpretation observed asymmetries profiles as function spatial position within sunspots. Spatial maps full Fe I 6302.5 A gathered large sunspots using HAO II instrument reveal that...

We characterize the observational properties of convectively driven vortex flows recently discovered on quiet Sun, using magnetograms, Dopplergrams, and images obtained with 1 m balloon-borne Sunrise telescope. By visual inspection time series, we find some 3.1 × 10−3 vortices Mm−2 minute−1, which is a factor ∼1.7 larger than previous estimates. The mean duration individual events turns out to be 7.9 minutes, standard deviation 3.2 minutes. In addition, several appearing at same locations...

We carry out a systematic search for extremely metal poor (XMP) galaxies in the spectroscopic sample of Sloan Digital Sky Survey (SDSS) data release 7 (DR7). The XMP candidates are found by classifying all according to form their spectra region 80AA wide around Halpha. Due size, method requires an automatic classification algorithm. use k-means. Our renders 32 having negligible [NII] lines, as expected galaxy spectra. Twenty one them have been previously identified literature -- remaining...

Models of galaxy formation predict that gas accretion from the cosmic web is a primary driver star over history. Except in very dense environments where mergers are also important, model galaxies feed cold streams penetrate their dark matter haloes. Although these predictions unambiguous, observational support has been indirect so far. Here we report spectroscopic evidence for this process extremely metal-poor (XMPs) local Universe, taking form localized starbursts associated with having low...

We measure the oxygen metallicity of ionized gas along major axis seven dwarf star-forming galaxies. Two them, SDSSJ1647+21 and SDSSJ2238+14, show ≃0.5 dex decrements in inner regions with enhanced star formation activity. This behavior is similar to drop observed a number local tadpole galaxies by Sánchez Almeida et al., was interpreted as showing early stages assembling disk galaxies, sustained external metal-poor accretion. The agreement tadpoles has several implications. (1) It proves...

Gas inflow feeds galaxies with low-metallicity gas from the cosmic web, sustaining star formation across Hubble time.We make a connection between these inflows and metallicity inhomogeneities in star-forming galaxies, by using synthetic narrow-band images of Hα emission line zoom-in AMR cosmological simulations stellar masses M * 10 9 at redshifts z = 2-7.In ∼50 per cent cases lower than 4, gives rise to star-forming, Hα-bright, off-centre clumps.Most clumps have metallicities, weighted...

Massive high-redshift quiescent compact galaxies (nicknamed red nuggets) have been traditionally connected to present-day elliptical galaxies, often overlooking the relationships that they may with other galaxy types. We use large bulge-disk decomposition catalogues based on Sloan Digital Sky Survey (SDSS) check hypothesis nuggets survived as cores embedded inside haloes or disks of massive galaxies. In this study, we designate a "compact core" bulge component satisfies prescribed...

We describe the structural, stellar population and gas properties of nearest Ultra Diffuse Galaxy (UDG) discovered so far: UGC2162 (z=0.00392; R$_{e,g}$=1.7$(\pm$0.2) kpc; $\mu_g(0)$=24.4$\pm$0.1 mag/arcsec$^2$; g-i=0.33$\pm$0.02). This galaxy, located at a distance 12.3($\pm$1.7) Mpc, is member M77 group. has mass $\sim$2($^{+2}_{-1}$)$\times$10$^7$ M$_\odot$ embedded within cloud HI $\sim$10 times more massive: $\sim$1.9($\pm$0.6)$\times$10$^8$ M$_\odot$. Using width its line as dynamical...

ABSTRACT We investigate the contribution of clumps and satellites to galaxy mass assembly. analysed spatially resolved HubbleSpace Telescope observations (imaging slitless spectroscopy) 53 star-forming galaxies at z ∼ 1–3. created continuum emission line maps pinpointed residual ‘blobs’ detected after subtracting disc. Those were separated into compact (unresolved) extended (resolved) components. Extended components have sizes ∼2 kpc comparable stellar age as discs, whereas are 1.5 dex less...

view Abstract Citations (128) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Line Asymmetries and the Microstructure of Photospheric Magnetic Fields Sanchez Almeida, J. ; Landi Degl'Innocenti, E. Martinez Pillet, V. Lites, B. W. A systematic structuring magnetic fields over scales much smaller than mean free path photospheric photons may be responsible for observed asymmetrical Stokes profiles. We explore this possibility by deriving...

Using the 'k-means' cluster analysis algorithm, we carry out an unsupervised classification of all galaxy spectra in seventh and final Sloan Digital Sky Survey data release (SDSS/DR7). Except for shift to restframe wavelengths, normalization g-band flux, no manipulation is applied original spectra. The algorithm guarantees that galaxies with similar belong same class. We find 99 % can be assigned only 17 major classes, 11 additional minor classes including remaining 1%. not unique since many...

Tadpole galaxies, with a bright peripheral clump on faint tail, are morphological types unusual in the nearby universe but very common early on. Low mass local tadpoles were identified and studied photometrically previous work, which we complete here analyzing their chemical dynamical properties. We measure Halpha velocity curves of seven tadpoles, representing 50% initial sample. Five them show evidence for rotation (sim 70%), sixth target hints at it. Often center is spatially offset...

We present a visual determination of the number bright points (BPs) existing in quiet Sun, which are structures though to trace intense kG magnetic concentrations. The measurement is based on 0.1 arcsec angular resolution G-band movie obtained with Swedish Solar Telescope at solar disk center. find 0.97 BPs/Mm^2, factor three larger than any previous estimate. It corresponds 1.2 BPs per granule. Depending details segmentation, cover between 0.9% and 2.2% surface. Assuming their field...

Local UV-bright galaxies in the Kiso survey include clumpy systems with kpc-size star complexes that resemble young surveys at high redshift. We compare clump masses and underlying disks several dozen from each of these to normal spirals. Photometry spectroscopy for spiral sample come Sloan Digital Sky Survey. find largest UDF clumpies terms formation rates, masses, surface densities. Clump densities spirals are smaller. If proportional turbulent Jeans mass interstellar medium, then most...

Local star-forming galaxies show properties that are thought to differ from in the early Universe. Among them, ionizing stellar populations and gas geometry make recipes designed derive chemical abundances nebular emission lines those calibrated A sample of 1969 Extreme Emission Line Galaxies (EELGs) at a redshift 0 < z 0.49, selected Sloan Digital Sky Survey (SDSS) be local analogues high-redshift galaxies, was used analyze their most prominent total oxygen nitrogen-to-oxygen ratios...

We present spectropolarimetric observations of internetwork magnetic fields at the solar disk center. A Fabry-Pérot spectrometer was used to scan two Fe I lines 6301.5 and 6302.5 Å. High spatial resolution (05) magnetograms were obtained after speckle reconstruction. The patches with above noise cover approximately 45% observed area. Such large coverage renders a mean unsigned flux density some 20 G (or Mx cm-2), which exceeds all previous measurements. Magnetic signals occur predominantly...

We analyze a time sequence of Inter-Network (IN) magnetograms observed at the solar disk center. Speckle reconstruction techniques provide good spatial resolution (0.5" cutoff frequency) yet maintaining fair sensitivity (some 20G). Patches with signal above noise cover 60% area, most which corresponds to intergranular lanes. The large surface covered by renders mean unsigned magnetic flux density between 17G and 21G (1G \equiv 1Mx cm$^{-2}$). difference depends on spectral line used generate...

High-resolution G-band images of the interior a supergranulation cell show ubiquitous bright points (BPs; some 0.3 BPs per Mm2). They are located in intergranular lanes and often form chains elongated blobs whose smallest dimension is at resolution limit (135 km on Sun). Most them live for few minutes, having peak intensities from 0.8 to 1.8 times mean photospheric intensity. These probably tracing intense magnetic concentrations, existence has been inferred spectropolarimetric measurements....

The paper describes an automatic inversion code to recover microstructured magnetic atmospheres (MISMAs) by fitting Stokes profiles. These solar model incorporate small-scale fluctuations of the field vector, velocity, temperature, etc., which seems be intrinsic property photosphere. MISMAs considered for have several distinct components. Each one them is made slender flux tubes, so that whole vertical stratification MISMA reconstructed from a finite set parameters. has been thoroughly...